There are also chapters for Arya, Sansa/Alayne, and Aeron Greyjoy written for ADWD but moved to TWOW, though none of those have been read at conventions or made available as samples yet. Which means that virtually all of the 200 manuscript pages Martin had completed as of the middle of last year was stuff he'd already had when he started work on the book.

Two more years, and he essentially has had the first 200 pages or so already finished for a year? Yikes...

yeah, his odds of finishing the series before GoT show ends are slim to none. Kinda steals his thunder if the tv show spoils his end before he gets to write it. Even if they go in a different direction than he does, it's not really a positive for him...

Well, he doesn't give updates on his progress anymore, except "I'm working on it" ... So who knows, maybe he writes 50 pages a day or maybe he got stuck with the next Meereenese knot. Yeah, we'll probably get the end of the story from the TV show.

^
It all depends on the related question, how many seasons will the show run for. Two seasons for Storm of Swords... which suggests anywhere between two and four for the presumed combination of A Feast for Crows/A Dance with Dragons. And then anyone's guess how many seasons the last two books are, and this is all assuming the show doesn't get cancelled for whatever reason at some point (or deal with cast disputes - the've already had to write off notable minor characters, after all).

^Agreed. There's also the possibility of the TV series taking a year off between seasons, as HBO shows sometimes do. I think Benioff and Weiss have said they anticipate an eight or nine season run, which suggests they expect to spend more than one season on at most one of the four post-Storm books. They may also be thinking of combining Feast and Dance into a single season (perhaps with a little spillover into the seasons preceding and following)-- even given their combined page count, it's hard to imagine getting two years' worth of satisfying story out of those books, let alone more.

^
I sure hope they are considering condensing those two novels into one season - I think the highlights of AFFC and ADWD could be worked into one solid season (and it would inevitably lose much of the padding), but I don't know how likely that is.

The question is whether Benioff and Weiss' solution to the pacing problems of those two books is to condense, or to contrive more "dramatic" variant storylines to make them fill multiple seasons naturally. Their approach to the Daenerys material in season two suggests they might be open to the latter. And they have to be thinking about how to avoid catching up to the books; I imagine that taking a freer hand with adaptation of Feast and Dance would feel preferable to making things up entirely based on the few details of Winds and Dream Martin has shared with them.

Enough for a fourth and a fifth season at the very least; more if they decide to adapt the most recent books over multiple seasons. I imagine there'll be another book published before they run out of material; the issue is going to be when that book has been adapted and the final one is still two or three years away.